More rain delays so getting an early jump on ideas for later.

Have decided to mount an Augermate to my seed wagon.

The newer larger wagons are designed to accept the mounts on the end steel frame work like this pic found on the web.

The ends and side piece metal structures on my older wagon I do not feel are heavy enough or thick enough to support the bracket and Augermate as it is really pretty heavy and is not even filled with 5 gallon of hydraulic oil, gas and motor oil yet. My idea for a sliding tray does not seem feasible under the front slope of the box as there is just not quite enough height to allow clearance. I could possible separate the gear from the box and install the Augermate in this area from the bottom up on a recessed  platform between the stringers but it would still be cramped for fueling, checking oil, and servicing.

Was thinking of attaching the mounting frame to the side of the wood wagon runner but am concerned with drilling additional cross holes through the wood beam.

Where is the significant load and or weakest point in this wood runner ?

There are 1/2" holes at the 2 yellow arrow locations.

There are 7/16" holes at the 2 red and 2 green arrow locations that bolt the box to the runner.

The 2 end supports of the box are actually beyond the ends of the front and rear axle of the gear. This lessens the span of the runner and actually cantilevers the load some past the axles tending to pull up in the center of the runner.

Is the wood beam similar to a truck frame where the holes should only be horizontally through the member instead of vertically through the top and bottom of the beam ?

Was considering bolting a channel iron to the side of the runner utilizing the existing holes at the green arrows and drilling 2 new holes at the blue arrows.  Will that cause issues or weaken anything more structurally than the existing holes ?

Next will there be significant rotating force on the beam ? and does that means it should be tied into the other side by cross supports to counteract this force rotating the runner and pulling downward ?

Overall this looks more accessible on the side than under the front.

Thoughts,ideas or suggestions ?